Get purchase code from Themeforest:
Log in your Themeforest account. Then go to downloads. Here you will find all of your purchased products. You can get purchase code of any products purchase code by clicking on that products download button, then click License certificate & purchase code.
Activate by purchase code:
After install the theme. It will automatic redirect you to the theme about page, where you put the purchase code & activate theme. Then you need to enter the purchase code on the text field & click Activate button to activate the theme.
After activating theme, it will show you a success screen. Finally now you are eligible to use the theme. you can deactivate the license by clicking Deactivate button when you want.